The purpose of this research is to examine the development in ontogeny of: (1) defensive predisposition, (2) affinitive bonds, (3) socialization through play, (4) feeding habits and their effects in the adult cat on: (a) where the cat falls on a previously demonstrated continuum of predisposition to respond defensively to environmental threat (Adamec, 1975a), (b) adult predatory aggression which varies inversely with this predisposition (Adamec, 1975a), and (c) the neural substrate of this defensive predisposition which has already been examined in some detail in adult cats (Adamec, 1975b, 1975c). The early experience of kittens is being modulated by early selective exposure to several environments: (1) social isolation, (2) repeated observation of an adult's (cat) predatory attack on adult rats with normal litter rearing,(3) eight hours of daily exposure to adult male hooded rats to promote affinitive bonding to potential prey. Kuo (1930) has demonstrated that the rearing environments described above alter adult predatory disposition to various prey types--most probably by modulating predisposition to respond defensively to prey, or through positive social bonding to prey species with which they have lived. Defensiveness responsiveness appears measureable neurally as the ease with which certain brain (limbic) circuits can be thrown into oscillation by an exogenous (electrical) stimulus. These brain measures are an aspect of the kindling phenomenon originally described by Goddard (1969). The behavioral analysis of kitten and adult behaviors will delineate what aspects of early experience (interaction with the environments described above) are responsible for variation in defensiveness and in limbic system excitability. In a most general sense we are trying to quantify behavioral and experiential antecedents of the physiological basis of a personality trait (behavioral disposition). BIBLIOGRAPHIC REFERENCES: Adamec, R. (1975a). The behavioral bases of prolonged suppression of predatory attack in cats. Aggressive Behavior, 1, 297-314. Adamec, R. (1975b). The neural basis of prolonged suppression of predatory attack, I. Naturally occurring physiological differences in the limbic systems of killer and non-killer cats. Aggressive Behavior, 1, 315-330.